Add github action to check formatted code

[duarte-pompeu]

The best approach would be to create a PR with the formatted code.

Useful references:

https://github.com/marketplace/actions/create-pull-request

https://peterevans.dev/posts/github-actions-how-to-automate-code-formatting-in-pull-requests/

[duarte-pompeu]

Partially achieved by #10 , but sending a PR would be nicer.